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Wednesday, 29 May 2013

Cicada Killer Wasp

Does exactly what it says on the tin! Such honesty is scant comfort if you're a Cicada.
Cicada Killers are about 20 species in the genus Sphecius, that can be found across the world in tropical and some temperate climes. North America's Eastern Cicada Killer (S. speciosus) seems to be the one that has most captured our malicious, little hearts.

These are large wasps; the females may be 5 cm (2 in) long, the males a little smaller and quite a lot lighter. They can be seen sucking up nectar from flowers, using the sugar rush to keep those wings buzzing like an over-excited child at a birthday party.

But they can also be seen doing something significantly less palatable. The Cicada Killer Wasp kills Cicadas! There are no red herrings here. You're reading a murder mystery called "The Butler Did It" and the butler did indeed do it.

It all begins when a whole load of Cicada Killer Wasps emerge from their burrows for the very first time. In the heat of the sun, it's time to get frisky. Males are extremely aggressive with each other, fighting both on the ground and in mid-air over females to mate with. They might even continue fighting while a male is in the very act of mating! Some guys just can't take a hint...

It's good that the males can't sting otherwise they'd probably just kill each other. Females do have venom, but they are thankfully uninterested in humans. These wasps are solitary, not social, so without a huge nest full of sisters, grubs, food and a queen, they simply have better things to do.

After fighting and mating, the males promptly lie on their back, put their feet up and relax. By which I mean die.

For the females, however, life has barely begun. And it's a life of toil and labour punctuated by nectar to take the edge off. She must first get digging, burrowing a good 30 to 60 (foot or two) into the ground. This is just the kind of burrow she herself emerged from.

Cicadas can easily be as big as their Killer and a lot heavier due to their more robust shape. They can't do much to defend themselves other than get really loud and annoying, and once the venom takes its toll, the struggle ceases.

Now the Cicada Killer undertakes the arduous journey back to her burrow. She pulls it and drags it and heaves it and hefts it all the way home. She might even fly for short bursts if she can, but its exhausting work.

And now you know why the Emerald Cockroach Wasp zombifies her prey instead of paralyses it. It's so much easier if that thing can walk!

She takes the Cicada deep into her burrow and drops it off. Her burrow may have several, separate rooms into which she will lay a single egg. The Cicadas serve as a substantial, nourishing meal for growing grubs, so each room is provisioned with one Cicada for a male and two or three for a female.

So now our doting mother must go on the hunt once more, probably sipping some more nectar for energy and respite from the terrible working conditions. She doesn't even get a pension! Once all her work is done, she simply dies and never sees her children grow and pay her back for the food and housing she provided them.

Meanwhile, in the burrow, the eggs hatch and a tiny grub wakes up to the sweet scent of food. They eat, they grow and they might even spend the winter months down there. Soon enough, they pupate and an adult Cicada Killer emerges.

So what's the sting in the tail? Did the butler really do it? Who is the true Cicada Killer?

It's the larva.

The Cicada Killer Wasp we see buzzing around is a mere accomplice, paralysing the Cicada and serving up the unmoving body to her children. It's the larva who does the killing, who eats the Cicada to death in the quiet, untroubled darkness of the burrow.

Be thankful that an over-excited child at a birthday party only gets really loud and annoying...